CPU fan is constant max RPM when power is off - Aspire TC-865-UR14

Very odd but when my Aspire TC-865-UR14 goes in to sleep mode or I power down, within a second the CPU fan cranks up to its maximum speed and stays there until I either unplug or power up again. Is there some sort of malfunctioning relay switch I could replace on the mother board? This may seem strange but I had a similar problem with the radiator cooling fan on my car and found that in the fuse box there was a $15 relay switch that I could just unplug and plug the new one in. I figure if I can find something in the mother board like that I may need to get out the soldering gun to replace it, but it probably isn't the CPU fan itself its some temperature sensor of some sort malfunctioning.

//Edited the content to add model name.

Accepted answers

Larryodie

Seems to be a SMC chip issue. Note page 3 also note that this is a laptop.

https://community.acer.com/en/discussion/comment/921518#Comment_921518

https://community.acer.com/en/discussion/comment/1008170#Comment_1008170

You may need to do a visual to see what is the part # of the SMC chip if it is labeled ?

Larryodie

You may get lucky and find an overheated (cracked) chip. You need hot air or Chip Quik, Flux if the part # is readable.
I would turn it on/off as you're doing with a strip or run a fan wire to an external toggle switch to just cut off the fan.

All comments

Easwar

Hi @cdob,

It looks like hardware issue. Contact acer tech support,

https://www.acer.com/ac/en/US/content/service-contact

OR book the unit for repair service,

https://customerselfcare.acer.com/CS2/#/

Larryodie

I'd reset the bios or by doing a F9, reset and clean the connector on the fan unit. By all means, give your unit a good cleaning and Disable Fast Start before you send off for repair or start trouble shooting for a bad sensor, I doubt that a relay is used ? It may be Fast Start along with a lots of dirt blockage that is keeping it going ? https://www.windowscentral.com/how-disable-windows-10-fast-startup

billsey

Yes, the fan speed is controlled by the BIOS and everything still runs under power until the CPU temperature drops when you do a shutdown or sleep. It sounds as if the BIOS is either seeing a high CPU temp that's bogus or it's got a bogus value for the needed low temp. Either way might fire the fan up at full speed...

Larryodie

For Information purposes only, The "Smart Fan " can be turned off and then the fan will not vary.

20211022_124557.jpg

billsey

Good to know, some models have that function in the BIOS and some do not.

cdob

I tried turning off fast start in Windows, no difference so I put it back on.

I tried turning of Smart fan in the bios, then the fan didn't vary anymore, the fan was cranked up to full speed all the time

So that is now enabled again.

I tried a good cleaning before posting, and reseating the wire from the fan to the board before posting, no luck.

Thanks for the suggestions, I'm going to try searching out a schematic for the motherboard itself, I'd probably just buy a new motherboard rather than deal with tech support.

ttttt

@cdob

I think changing the CPU fan will solve the issue.

Larryodie

Seems to be a SMC chip issue. Note page 3 also note that this is a laptop.

https://community.acer.com/en/discussion/comment/921518#Comment_921518

https://community.acer.com/en/discussion/comment/1008170#Comment_1008170

You may need to do a visual to see what is the part # of the SMC chip if it is labeled ?

cdob

I just watched a youtube video of replacing an SMC chip . . . . . . I now recognize I do NOT have that skillset or the tools that would be required, even if I knew which one to replace on this motherboard.

I ordered a new CPU fan from amazon, tried that but didn't help. I think the SMC chip sounds more likely but I'll have to just keep turning off my power bar after I shut down.

Thanks so much for all the advice.

Larryodie

You may get lucky and find an overheated (cracked) chip. You need hot air or Chip Quik, Flux if the part # is readable.
I would turn it on/off as you're doing with a strip or run a fan wire to an external toggle switch to just cut off the fan.

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